Filter aid slurry metering process

ABSTRACT

A system for measuring the solids content on a dry basis in a filter aid water slurry and pumping the filter aid back into a filter is described herein. The system circulates the filter aid water slurry through a density gauge and flowmeter to measure the dry weight of solids therein. Then, the slurry is pumped back into the filter for reuse.

[ 51 July 18,1972

[54] FILTER AID SLURRY METERING PROCESS James A. King; David R. Maxam,both of Green River, Wyo.

Stauffer Chemical Company, New York, NY.

Filed: Sept. 25, 1970 Appl. No.: 75,587

Inventors:

Assignee:

US. Cl 210/75, 210/96, 210/193 Int. (I B011! 37/02 Field of Search..2l0/75, 96, I93

References Cited UNITED STATES PATENTS 3,349,91310/1967 Schneider3,362,533 H1968 Muller ..2l0/75 Primary Examiner-Jim L. DeCesareAttorney-Daniel C. Block, Edwin H. Baker, Albert J. Adamcik and Harry A.Pacini [57] ABSTRACT A system for measuring the solids content on a drybasis in a filter aid water slurry and pumping the filter aid back intoa filter is described herein. The system circulates the filter aid waterslurry through a density gauge and flowmeter to measure the dry weightof solids therein. Then, the slurry is pumped back into the filter forreuse.

3 Claim, 1 Drawing Figure FIGURE INVENTOR. JAMES A. K I N 6 DAVID R.MAXAM ATTORNEY FILTER AID SLURRY METERING PROCESS BACKGROUND OF THEINVENTION In the art of extracting soda ash from Wyoming. Trona, it isthe practice to heat the crude trona in a calciner and convert the tronato sodium carbonate. The calcined sodium carbonate is then dissolved ina dissolver. The dissolver contains insolubles in addition to the sodiumcarbonate in solution. The material from the dissolver is transferred toa rake classifier where substantially all of the insolubles are removed.The solution coming from the rake classifier is conveyed to a thickener,wherein additional solids that were not removed in the rake classifierare removed. The overflow from the thickener will contain a small amountof insolubles that must be removed. The overflow from the thickener isconveyed to a leaf pressure-type filter, wherein the insolubles areremoved. The leaf pressure-type filter uses as a filter aid,diatomaceous earth or perlite.

When the pressure drop across the leaf pressure-type filter becomes toogreat, it becomes necessary to recharge the filter with new diatomaceousearth or perlite. Thus, the insolubles and filter aid were usuallydumped and the new filter aid was inserted into the leaf pressure-typefilter. This resulted in substantial loss of the filter aid material,since the filter aid and insolubles could not heretofore be separated.However, a commercial separation apparatus has now been perfected whichwill separate the insolubles from the filter aid medium. The filteraidcan now be reclaimed for additional use. Thus, the underflow from theseparation apparatus will be a water slurry of the filter aid medium. Inorder to reuse the filter aid, it becomes necessary to manually measurethe density of the slurry and then calculate the content thereof of thefilter aid on a dry basis. Once the calculation has been made the slurrycan be metered out by volume back into the system for reuse of thefilter aid medium. As is apparent, the manual measurement of the densityand the calculation of the amount of filter aid within the filter aidwater slurry is subject to error and is a time-consuming operation.

BRIEF DESCRIPTION OF THE INVENTION It has been discovered that ametering system can be readily employed and used to automaticallymeasure the filter aid contents of the filter aid water slurry on a drybasis and pumped or metered back into the system automatically, whichsubstantially eliminates the error and time-consuming manual operation.This is brought about by synchronizing a magnetic flowmeter with adensity gauge in a unique manner, such that the signal from the twometers are read out on a totalizing meter in a distribution system. Thefilter aid slurry is accurately determined on a dry basis; that is tosay, the number of pounds per unit volume within the slurry isaccurately measured and pumped back into the system for. reuse.

BRIEF DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTIONIn the practice of the present invention, the filter aid slurry that hasbeen reclaimed for reuse is conveyed to a storage or holding tank 1 viaconduit 2. At the bottom portion of tank 1, conduit 3 fluidlycommunicates therewith and is connected to the inlet of pump 4. Fluidsflowing through conduit 3 is controlled by valve 21. Intermediate thepump 4 and tank I conduit 22 fluidly communicates with conduit 3 withthe flow of fluids therethrough being controlled by valve 23. Thepurpose of conduit 23 will be set forth hereinafter. The outlet frompump 4 is connected to a magnetic flowmeter 6 by conduit 5. F lowmeter 6is connected to an automatic density gauge 7 by conduit 8. The gauge 7is connected to a branched pipe 10 by conduit 9. One branch of conduit10 fluidly communicates with the tank 1 with the flow of fluidstherethrough being controlled by valve 12. The other branch of conduit10 is connected to a filter aid mixing tank with the flow of fluidstherethrough being controlled by valve 11.

The gauge 7 functions to measure the density by absorption of gammaradiation. The absorption of gamma radiation depends on the thicknessanddensity of the process material, thickness and density of the processconduit, thickness and density of insulation on the conduit, and energyof the gamma radiation. Since all of these factors, except density ofthe process material remain constant, the gauge measures the density ofthe process material. The radiation source and detector are arranged sothat the radiation is directed along the axis of a straight section ofconduit. The radiation is provided by a gamma source. The detector is atemperature regulated ionization cell. The density gauge is mounted sothat the radiation passes through the diameter of the pipe. Mountingbrackets are provided so that the gauge can be coupled onto an existingconduit. The ionization cell, when exposed to gamma radiation, generatesa current which can be measured. Thus, line 18 connects the ionizationcell of gauge 7 with an amplifier 15. The current generated is fed intoa totalizer 16. It should be noted that the gauge 7 is commerciallyavailable and is sold by Ohmart Company of Cincinnati, Ohio.

The magnetic flowmeter 6 consists of a low transmitter connected bycable 17 to the receiver 14. The flow transmitter consists of anon-magnetic tube through which the liquid flows, an electricalinsulating liner on the inside of the tube, and an electro magnet whichinduces a magnetic field through the tube and two magnetic electrodeswhich are essentially flush with the inside surface of the tube andwhich contact the following liquid. The output of the transmitter islinear and is directly proportional to the average velocity of theflowing liquid which is, in turn, proportional to volume flow rate. Itwill operate accurately in any position so long as the line iscompletely filled. The output of flowmeter 6 is conveyed by cable 17 tothe receiver 14 which is conveyed to the totalizer 16. The totalizer l6integrates the signals from the amplifier l5 and receiver 14 to auseable digital readout. This digital reading is approximately theactual weight of the filter aid material on a dry basis necessary torecharge a filter for a production cycle. The magnetic flowmeter 6 andthe receiver 14 are commercially available and sold by the FoxboroCompany of Foxboro, Mass. The totalizer 16 is also commerciallyavailable and sold by Leeds & Northrup of Pennsylvania.

In operation, the filter aid water slurry is conveyed to the tank 1 viapipe 2. The percent solids in this tank may vary from about 8 to 20percent by weight. When it is desired to recharge the leaf type filter,the pump 4 is started and valves 12 and 21 are opened. This allows theslurry to circulate through the gauge 7 and flowmeter 6 and back intothe tank 1 as indicated by arrow 19 until such time as the density gauge7 can level out. When the density gauge 7 reads a constant value, valve12 is closed and valve 11 is opened, which will convey the slurry to thefilter aid mixing tanks, as indicated by the arrow 20. The integratedcircuit in the totalizer 16 receives signals from the density gauge 7and magnetic flowmeter 6. This circuit totalizes the number of pounds offilter aid on a dry basis flowing to the mix tank. The system senses anychange in density and/or flow and will automatically make adjustmentsfor any variation of these parameters. The number of pounds of filteraid are totalized on a counter located on totalizer 16. When therequired amount of filter aid has been pumped, the pump 4 is stopped andvalves 21 and 11 are closed. The valve 12 is opened and water is pumpedthrough line 22 with valve 23 being opened for a short period of time toinduce flushing water. After the lines have been sufficiently flushed,the conduit 3, 5, 8 and 9 are left packed with water. This is necessaryto keep the gauge 7 and meter 6 in good operating condition.

As can be seen from the above description, a system is provided whichautomatically measures the filter aid contents of a filter aid waterslurry on a dry basis and meters and pumps the slurry back into thesystem automatically. It is essential to the practice of this inventionthat the density gauge 7 and flowmec. measuring the solids content ofthe slurry on a dry weight ter 6 work in unison within the circuit toprovide the result basis; achieved herein. d. totalizing the solidscontent of said slurry;

We claim e. delivering the metered slurry to a system for reuse.

1. In a process for using filter aid in a filter aid water slurry, 2.The process as set forth in claim 1 wherein the totalizing comprising thSteps f; is brought about by synchronizing the flowmeter and density a.delivering the filter aid water slurry from a reclaim g 3. The processas set forth in claim 1 together with the additional step of packing theflowmeter and density gauge with 10 water after use.

process to a holding means; b. circulating the filter aid water slurryfrom the holding means through a flowmeter and density gauge and backtotheholdingmeans; a at

2. The process as set forth in claim 1 wherein the totalizing is broughtabout by synchronizing the flowmeter and density gauge.
 3. The processas set forth in claim 1 together with the additional step of packing theflowmeter and density gauge with water after use.